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The following article by ScienceDaily reported on a paper in Psychological Science (Mrazek et al., 2013), claiming that mindfulness training led to improved working memory and GRE scores. These studies always pique my interest, but there is always some hole in it that makes me think "Waait a minute!"

In the case of the present study, my concern is that participants in the experimental condition were required to practice mindfulness in their daily lives, while those in the control nutrition condition were not required to alter their diet. The concern is whether the improvement came from practicing mindfulness, or from practicing something, but this is not my area, and it could be that prior research has already accounted for that somehow. Usually I would leave it at that, but this seems well suited for my first CSci.SE question.

My full question is thus: What is the state of the field regarding the effect of practicing meditation on cognition, over and above other forms of practice?

1 Answer
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General Review of Mindfulness Meditation on Cognitive Performance

There is a review article Chiesa et al (2011) which would provide a good starting point. They review 23 studies looking at the effect of mindfulness meditation on performance on objective cognitive tests.

Twenty
three studies providing measures of attention, memory, executive
functions and further miscellaneous measures of cognition were
included. Fifteen were controlled or randomized controlled studies and
8 were case–control studies. Overall, reviewed studies suggested that
early phases of mindfulness training, which are more concerned with
the development of focused attention, could be associated with
signiﬁcant improvements in selective and executive attention whereas
the following phases, which are characterized by an open monitoring of
internal and external stimuli, could be mainly associated with
improved unfocused sustained attention abilities. Additionally, MMPs
could enhance working memory capacity and some executive functions.
However, many of the included studies show methodological limitations
and negative results have been reported as well, plausibly reﬂecting
differences in study design, study duration and patients' populations.
Accordingly, even though ﬁndings here reviewed provided preliminary
evidence suggesting that MMPs could enhance cognitive functions,
available evidence should be considered with caution and further high
quality studies investigating more standardized mindfulness meditation
programs are needed.

In general I take a very sceptical perspective on the potential capacity of mindfulness meditation to improve cognitive performance. A lot of research shows that IQ is difficult to manipulate, and that much of what we learn is domain specific and is developed by practicing or learning about that particular domain. That said, I would be somewhat more open to the idea that mindfulness meditation might improve capacity for attention or motivation control.

Review of Mrazek et al

The study used several measures of cognitive performance. Notably verbal GRE and working memory were both used. Significantly greater improvements (pre versus post) were found in the mindfulness condition relative to the control nutrition condition.

I am generally sceptical that mindfulness meditation could lead to a lasting improvement of something as grand as a verbal ability factor. While it is possible that the program was effective, I would expect there is an alternative explanation.

The first issue is the small sample size (albeit the pre-post element of the design is good). There were only 48 participants. There has been ample discussion of issues with small sample experimental studies like this. It is easier for small sample studie to be conducted, and therefore they are more likely to be published when effective. Type 1 error is an explanation. Likewise, without wanting to cast dispersions on any one study, broadly there is greater potential in small sample studies for little analysis decisions to dramatically increase the potential for a Type I error rate to arise (see for example the discussion of the effect of flexibility in data analysis by Simmons et al 2011).

Similarly, even in the absence of any flexible analytic strategies, there still is the publication bias towards statistically significant and interesting findings.

Mindfulness participants appear to have improved verbal GRE accuracy from around 43% to around 53%. This is probably close to a one standard deviation improvement in verbal ability. Even if mindfulness meditation was effective, it seems a little implausible to expect such a large increase given how presumably an equivalent increase might take three or four years of education to achieve with traditional means.

Even if the finding was replicable, an alternative interpretation would be that the effect was due to some form of effort related factors that varied based on condition (e.g., some form of placebo - effort interaction).

Putting the small sample to one side, this appears to be a well-designed study. That said, based on my prior understanding of mechanisms of cognitive change and the many alternative interpretations mentioned above for the findings, I am not persuaded that mindfulness meditation is effective in changing verbal ability.